Malcolm Betts

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G.805 and G.800ITU-T functional model of
transport networks

• Malcolm Betts
• Rapporteur Q.12/15
• Nortel Networks, Canada

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Topics

• History
• What is a functional model
• Evolution

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History

• Work started in 1989, the first Recommendation
  (G.803) was approved in 1992
• SDH networks with PDH interfaces
• First customer Network management
• Generalized to cover connection oriented (point
  to point) transport networks
• G.805 approved in 1996
• Generalized to cover connection oriented and
  connectionless
• G.809 connectionless architecture approved 2003
• G.800 unified connection oriented/connection less
  architecture approved in 2007
• Continuing to evolve
• Basic concepts stable since 1990

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Box view of an EPL service
SDH ADM
SDH Xcon
SDH Xcon
SDH ADM
ETH PHY
ETH PHY
STM-16 Line
STM-64 Line
STM-16 Line
Term
Term

• Difficult to understand the network topology
  without understanding the details of all the NEs
• The model is specific to the actual NEs being
  used
• Collapses collocated end points into a single
  point

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Why use a functional model

• OSI 7 layer model is not a good fit for transport
  network
• Multiplexing hierarchy
• Many layer provide the same function i.e.
  transport
• e.g. DS-1 DS-3 VC-4 STM-N
• Inverse multiplexing (e.g. Vcat)
• Transport network
• Multi domain
• carrier
• administrative within a carrier e.g.
  maintenance regions
• Multi Technology
• Multi vendor

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What is a functional model

• A modeling language to describe the forwarding
  aspects of transport networks
• In terms of information transfer capability
• In a technology-independent manner
• Using a small set of components
• Relates the equipment/logical resource/FCAPS
  views
• Functional models are useful to design and manage
  networks
• Common model structure for all technologies that
  are in the transport network
• Key concepts
• Layer networks
• Partitioning (of layer networks)
• Recursion
• Reuse of the basic patterns

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Functional model of an EPL service
GFP
VC-4-7vc
Eth PHY
Eth PHY
VC-4
STM-16
STM-16
STM-64
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Layer Networks
Client (layer network)
Forwarding Point

• Adaptation
• Multiplexing, rate adjustment
• identification of clients

• Access point
• Adapted Information (AI)

The access point is an abstraction barrier that
provides layer network independence

• Termination
• Adds Layer Information (LI)
• Overhead for monitoring
• Identification of access point

Server (layer network)

• Forwarding End Point
• Characteristic Information (CI)
• CI AI LI

• CI defines the Type of layer network
• The set of access points defines the instance
  of the layer network

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Layer Network recursion
Client (layer network)
e.g. DS-1
Server (layer network)
Client (layer network)
e.g. DS-3
Server (layer network)
e.g. VC-3
Client (layer network)
Server (layer network)
e.g. STS-12
Client (layer network)
Server (layer network)
e.g. OC-12
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Layer network topology

• Subnetwork
• Flexible connectivity
• A switching matrix/router (at the limit of
  recursion)

• Link
• Fixed connectivity between subnetworks
• Supported by a fiber at the bottom of the layer
  recursion

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Layer network - Connection
Trail
Subnetwork connection
Termination Connection Point
Connection Point
Link connection
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Partitioning of a subnetwork
Subnetwork
Subnetworks Links
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Recursive partitioning of a subnetwork
Subnetwork
Subnetworks Links
Subnetwork
Subnetworks Links
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How is a functional model used- Partitioning

• Provides a uniform model of the topology (links
  and subnetworks) that allows the inner details of
  one operators network to be invisible to an end
  user or another network
• Basis of the domain concept in the ASON
  architecture G.8080
• Different domains may use different approaches
  for connection management
• Fault detection to isolate a fault to a domains
• Independent survivability actions per domain
• Provides independence between maintenance areas

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Support of Links
Client layer link
Client layer link connection
Client (layernetwork)
Server layer Trail
Server (layer network)
Link
Subnetwork
Link connection
Subnetwork connection
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Recursive client/server links
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How is a functional model used- Layering

• Provides a purpose specific view of the network
• The link hides the details of the server layer
  network or networks
• The characteristics of the server layer network
  can be abstracted as properties of the link
• Or
• Inter layer relationships can be navigated to
  reveal details if requirede.g. for multi layer
  connection management (control plane)
• Inter layer functions can be expanded to show
  interior detail e.g. for equipment models
• Reveal enough detail to provide inter operable
  implementations

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How is a functional model used- Layering and
Recursion

• A uniform model simplifies navigation across
  multiple technologies
• A server layer trail may support multiple
  different clients
• Network management systems must be able to
  configure or monitor any service over any infra
  structure
• e.g. Ethernet Virtual Private Line supported by a
  concatenation ofVLAN/Ethernet PHY - GFP/SDH
  Vcat/SDH nVC-4/SDH line pseudo
  wire/MPLS/GFP/OTN - VLAN/GFP/OTN - VLAN/Ethernet
  PHY
• Allows navigation (in an OSS) from a service
  (e.g. EVPL) to the bottom of the infrastructure
  that is used to provide that service e.g. a 10G
  wavelength

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G.800 Layer processor

• G.805 introduced the concept of a sub layer
• Support of tandem connection, SNC protection etc.
• Expansion of a connection point to introduce sub
  layer adaptation/termination functions
• G.800 has replaced sublayers with the Layer
  Processor function
• This allows access to or injection of LI at a
  location that is remote from a trail termination
• Makes the semantic context clear in a diagram
• A layer processor can only read or manipulate the
  LI it cannot read the AI

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Evolution

• G.805 used as basis for technology and
  application specific models
• Architecture
• G.803 (SDH), G.872 (OTN), G.8110 (MPLS) G.8110.1
  (T-MPLS)
• Equipment models
• G.783 (SDH), G.798 (OTN), G.8121 (T-MPLS)
• Management/control plane
• M.3100, G.774, G.85x.x
• TMF MTNM 814
• G.8080 (ASON)
• The functional model has been an integral part of
  the development of SDH and OTN

In the context of a transport network a control
plane is a distributed implementation of the
connection management function
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Evolution (contd)

• Connectionless (multipoint to multipoint) model
  G.809 approved in 2003 used as the basis for
  technology specific Recommendations now being
  migrated to G.800
• Ethernet Architecture
• G.8010 describes Ethernet in ITU terminology
• Ethernet Equipment and protection
• G.8021 (Ethernet), G.8031 (Ethernet)
• Network Management
• G.8010 provided the basis for Ethernet network
  management in TMF 814 v3.5
• Supports the integration of carrier Ethernet
  equipment and networks into the existing
  OSS/FCAPS infrastructure